Equation 15-15 says that for an ideal gas, \(C_p\) is greater than \(C_V\) by \(R = 8.314\mathrm{J}/ (\mathrm{mol} \cdot \mathrm{K})\), the ideal gas constant. The experimentally determined values of \(C_p - C_V\) given in Table 15-1 for real gases are very close to this theoretical prediction.